1. Field of the Invention
The present invention relates to a disk storage apparatus which specifically uses a low voltage power supply and has a head load and unload mechanism.
2. Description of the Related Art
Recently, a disk storage apparatus (disk drive) and, more specifically, a small sized hard disk drive is becoming more popular as an external storage apparatus of a personal computer, and also as a data storage apparatus of all kinds of digital devices. Small sized digital devices such as mobile information devices, including note book and note pad type personal computers, are different from stationary type computers such as desktop-type ones, or portable-types in that they are used in circumstances under which they are easily affected by external vibration or impact. Further, as the power supply for their operation, a low voltage power supply (for example, a 3.3 V power supply) is coming into common use.
In a small sized disk drive used for such small sized digital devices, countermeasures to vibration and impact, and reduction of power consumption are important design factors for making these products. As countermeasures to vibration and impact, a head load/unload mechanism and a magnet latch mechanism have been adopted. The head load/unload mechanism moves the headxe2x80x94at the time of non-operation such as during power shutdownxe2x80x94to a head stop member (also called parking member, or ramp parking member) positioned outside the range of the disk. The head load/unload mechanism then stops the head at a parking area on the stop member. This operation is called the unload operation or retract operation. Further, when the drive is started, the head is moved from the head stop member onto the disk. This operation is called the load operation.
In the disk drive, there is an actuator on which the head (a slider equipped with a read/write element) is mounted. The actuator is a mechanism which is rotationally driven between the position of the head stop member to a position on the inner periphery of the disk, along the diameter of the disk. Further, the actuator is driven by the driving force of a voice coil motor (VCM).
The magnet latch mechanism is a mechanism by which, at the time the head is subject to an unload operation, the latch plate attached to the VCM coil (drive section of the motor) is attracted by using the magnetic force of the magnet of the VCM, thereby latching the VCM coil. By this mechanism, the actuator is latched and the head can be held at the parking area. When in the parking area, the actuator comes into contact with a rubber member which is called the external-periphery-side stopper, thereby regulating the movement of the actuator toward the outside direction of the disk.
As described above, in small sized disk drives a strong mechanism for reducing the vibration or the impact is required as an important design consideration (in addition to reducing the power consumption). The mechanism to which both of the head load/unload mechanism, and the magnet latch mechanism, are associated, is the mechanism which counteracts the vibration or the impact.
Incidentally, when the magnet latch mechanism is used and the actuator motor (the VCM coil) is latched, a sufficient latch force is desirable in order to securely hold the head in the parking area to even during vibration and impact. On the one hand, because the power voltage level is decreased to reduce power consumption, the driving force (the VCM torque) of the VCM is relatively lowered. Accordingly, when the latch force (magnetic force of the magnet) of the latch mechanism is too strong, the latch of the VCM can not always be released at the start of the load operation.
Further, the movement of the actuator is limited by the outer periphery side stopper which is made of rubber material. However, the rubber material deteriorates with age, and the actuator thus sometimes is stuck on the deteriorated rubber. Further, it has also been confirmed that, changing the circumferential temperature lowers the VCM torque of the VCM below the rated one.
When the situation as described above occurs, even when the rated control current flows into the VCM at the time of the load operation, the actuator is not driven. Accordingly, the head can not be removed from the head stop member. That is, the head stop member has a continuously inclined surface (called a ramp) in the parking area which is a position at which the head stops. In the load operation, the actuator moves upward on the inclined surface. Depending on the condition (angle or shape) of the inclined surface, however, when the VCM torque falls below the rated amount, the driving force of the VCM becomes insufficient to move the actuator up the inclined surface, and there is a possibility that the actuator is stopped at a position on the inclined surface of the parking area.
Accordingly, an object of the present invention is to provide a disk storage apparatus, including a head load/unload mechanism and a latch mechanism, which is adapted for use with small sized disk drives of the low-voltage-power-supply type, and by which a stable load operation can be realized so that the head can be securely removed from a head stop member.
To achieve the above object, according to the present invention, there is provided a disk storage apparatus which includes a head load/unload mechanism, a latch mechanism, and which is adapted for use with the small sized disk drives of the low-voltage-power-supply type. The apparatus has a mechanism including a re-try processing operation which can be conducted when the head is stopped on the inclined surface in the parking area. In the re-try processing operation, the control current value is increased, and is supplied to the VCM when the control current of the rated current value (maximum current value) is supplied to the VCM and the load operation is started.
That is, the apparatus is provided with: a head stop member positioned at the outside of the disk, for maintaining the head in a stopped condition; an actuator mechanism for moving the head from the head stop member to the inner periphery of the disk by driving force of the voice coil motor (VCM); a motor drive control circuit having an additional power supply circuit by which a control current, whose current value is not smaller than the rated maximum current value, can be supplied to the VCM; and a control means for controlling the VCM, so that it is driven at a predetermined speed, by using the additional power supply circuit at predetermined conditions at the time of the load operation.
The predetermined conditions are when the speed of the VCM is monitored, a control current of the rated maximum current value is supplied, and the head is still stopped. In such the case, the control means uses the additional power supply circuit, supplies to the VCM a control current whose current value is added to the rated maximum current value, and conducts speed control of the VCM. The additional power supply circuit has a capacitor to accumulate the electric charge which is generated by stepping up the power supply voltage of the drive. Discharging the capacitor generates the additional current to be added to the control current.
With the above structure, even in the case of relatively low voltage power supply, the drive force (VCM torque) of the VCM can be temporarily increased. Accordingly, even when, for example, the actuator is attracted to the outer periphery side stopper, the head can be removed from the position of the head stop member. Further, even when the latch force of the latch mechanism is too strong, the actuator can be released. Further, even when the angle and shape of the inclined surface is sharp, the VCM can be driven with a force that ensures removal of the head from the position of the head stop member.